User`s manual

Chapter 1 Introduction AX2200/AX2300 Instruction Manual
1-6 CM2-AX2200-2001 (Rev. 4, 4/2014)
St =
f d
V
The Strouhal number is the other dimensionless number that quantifies the
vortex phenomenon. The Strouhal number is defined as:
Where
St = Strouhal Number
f = frequency of vortex shedding
d = shedder bar width
V = fluid velocity
As shown in Figure 1-3, AX2000Series meters exhibit a constant Strou-
hal number across a large range of Reynolds numbers, indicating a con-
sistent linear output over a wide range of flows and fluid types. Below
this linear range, the intelligent electronics in AX2000Series automati-
cally corrects for the variation in the Strouhal number with the Reynolds
number. The meter’s smart electronics corrects for this non-linearity via
its simultaneous measurements of the process fluid temperature and pres-
sure. This data is then used to calculate the Reynolds number in real
time. AX2000Series meters automatically correct down to a Reynolds
number of 5,000.
0.3
0.2
0.1
0.0
34
10
Linear range
Reynolds Number, Re
Strouhal Number, St
10
5
10 10
8
10
6
10
7
5000
Corrected range
Figure 1-3. Reynolds Number Range for the AX2000Series
Pressure Drop
The pressure drop for series AX2300 Insertion Meters is negligible. The pressure
drop for series AX2200 In-line Meters is defined as:
P = .00024  V
2
English units (P in psi,  in lb/ft
3
, V in ft/sec)
P = .000011  V
2
Metric units (P in bar,  in kg/m
3
, V in m/sec).